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      1 // Copyright 2013 the V8 project authors. All rights reserved.
      2 // Redistribution and use in source and binary forms, with or without
      3 // modification, are permitted provided that the following conditions are
      4 // met:
      5 //
      6 //     * Redistributions of source code must retain the above copyright
      7 //       notice, this list of conditions and the following disclaimer.
      8 //     * Redistributions in binary form must reproduce the above
      9 //       copyright notice, this list of conditions and the following
     10 //       disclaimer in the documentation and/or other materials provided
     11 //       with the distribution.
     12 //     * Neither the name of Google Inc. nor the names of its
     13 //       contributors may be used to endorse or promote products derived
     14 //       from this software without specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27 
     28 #ifndef V8CONFIG_H_
     29 #define V8CONFIG_H_
     30 
     31 // Platform headers for feature detection below.
     32 #if defined(__ANDROID__)
     33 # include <sys/cdefs.h>
     34 #elif defined(__APPLE__)
     35 # include <TargetConditionals.h>
     36 #elif defined(__linux__)
     37 # include <features.h>
     38 #endif
     39 
     40 
     41 // This macro allows to test for the version of the GNU C library (or
     42 // a compatible C library that masquerades as glibc). It evaluates to
     43 // 0 if libc is not GNU libc or compatible.
     44 // Use like:
     45 //  #if V8_GLIBC_PREREQ(2, 3)
     46 //   ...
     47 //  #endif
     48 #if defined(__GLIBC__) && defined(__GLIBC_MINOR__)
     49 # define V8_GLIBC_PREREQ(major, minor)                                    \
     50     ((__GLIBC__ * 100 + __GLIBC_MINOR__) >= ((major) * 100 + (minor)))
     51 #else
     52 # define V8_GLIBC_PREREQ(major, minor) 0
     53 #endif
     54 
     55 
     56 // This macro allows to test for the version of the GNU C++ compiler.
     57 // Note that this also applies to compilers that masquerade as GCC,
     58 // for example clang and the Intel C++ compiler for Linux.
     59 // Use like:
     60 //  #if V8_GNUC_PREREQ(4, 3, 1)
     61 //   ...
     62 //  #endif
     63 #if defined(__GNUC__) && defined(__GNUC_MINOR__) && defined(__GNUC_PATCHLEVEL__)
     64 # define V8_GNUC_PREREQ(major, minor, patchlevel)                         \
     65     ((__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) >=   \
     66      ((major) * 10000 + (minor) * 100 + (patchlevel)))
     67 #elif defined(__GNUC__) && defined(__GNUC_MINOR__)
     68 # define V8_GNUC_PREREQ(major, minor, patchlevel)       \
     69     ((__GNUC__ * 10000 + __GNUC_MINOR__) >=             \
     70      ((major) * 10000 + (minor) * 100 + (patchlevel)))
     71 #else
     72 # define V8_GNUC_PREREQ(major, minor, patchlevel) 0
     73 #endif
     74 
     75 
     76 
     77 // -----------------------------------------------------------------------------
     78 // Operating system detection
     79 //
     80 //  V8_OS_ANDROID       - Android
     81 //  V8_OS_BSD           - BSDish (Mac OS X, Net/Free/Open/DragonFlyBSD)
     82 //  V8_OS_CYGWIN        - Cygwin
     83 //  V8_OS_DRAGONFLYBSD  - DragonFlyBSD
     84 //  V8_OS_FREEBSD       - FreeBSD
     85 //  V8_OS_LINUX         - Linux
     86 //  V8_OS_MACOSX        - Mac OS X
     87 //  V8_OS_NACL          - Native Client
     88 //  V8_OS_NETBSD        - NetBSD
     89 //  V8_OS_OPENBSD       - OpenBSD
     90 //  V8_OS_POSIX         - POSIX compatible (mostly everything except Windows)
     91 //  V8_OS_SOLARIS       - Sun Solaris and OpenSolaris
     92 //  V8_OS_WIN           - Microsoft Windows
     93 
     94 #if defined(__ANDROID__)
     95 # define V8_OS_ANDROID 1
     96 # define V8_OS_LINUX 1
     97 # define V8_OS_POSIX 1
     98 #elif defined(__APPLE__)
     99 # define V8_OS_BSD 1
    100 # define V8_OS_MACOSX 1
    101 # define V8_OS_POSIX 1
    102 #elif defined(__native_client__)
    103 # define V8_OS_NACL 1
    104 # define V8_OS_POSIX 1
    105 #elif defined(__CYGWIN__)
    106 # define V8_OS_CYGWIN 1
    107 # define V8_OS_POSIX 1
    108 #elif defined(__linux__)
    109 # define V8_OS_LINUX 1
    110 # define V8_OS_POSIX 1
    111 #elif defined(__sun)
    112 # define V8_OS_POSIX 1
    113 # define V8_OS_SOLARIS 1
    114 #elif defined(__FreeBSD__)
    115 # define V8_OS_BSD 1
    116 # define V8_OS_FREEBSD 1
    117 # define V8_OS_POSIX 1
    118 #elif defined(__DragonFly__)
    119 # define V8_OS_BSD 1
    120 # define V8_OS_DRAGONFLYBSD 1
    121 # define V8_OS_POSIX 1
    122 #elif defined(__NetBSD__)
    123 # define V8_OS_BSD 1
    124 # define V8_OS_NETBSD 1
    125 # define V8_OS_POSIX 1
    126 #elif defined(__OpenBSD__)
    127 # define V8_OS_BSD 1
    128 # define V8_OS_OPENBSD 1
    129 # define V8_OS_POSIX 1
    130 #elif defined(_WIN32)
    131 # define V8_OS_WIN 1
    132 #endif
    133 
    134 
    135 // -----------------------------------------------------------------------------
    136 // C library detection
    137 //
    138 //  V8_LIBC_BIONIC  - Bionic libc
    139 //  V8_LIBC_BSD     - BSD libc derivate
    140 //  V8_LIBC_GLIBC   - GNU C library
    141 //  V8_LIBC_UCLIBC  - uClibc
    142 //
    143 // Note that testing for libc must be done using #if not #ifdef. For example,
    144 // to test for the GNU C library, use:
    145 //  #if V8_LIBC_GLIBC
    146 //   ...
    147 //  #endif
    148 
    149 #if defined(__BIONIC__)
    150 # define V8_LIBC_BIONIC 1
    151 # define V8_LIBC_BSD 1
    152 #elif defined(__UCLIBC__)
    153 # define V8_LIBC_UCLIBC 1
    154 #elif defined(__GLIBC__) || defined(__GNU_LIBRARY__)
    155 # define V8_LIBC_GLIBC 1
    156 #else
    157 # define V8_LIBC_BSD V8_OS_BSD
    158 #endif
    159 
    160 
    161 // -----------------------------------------------------------------------------
    162 // Compiler detection
    163 //
    164 //  V8_CC_CLANG   - Clang
    165 //  V8_CC_GNU     - GNU C++
    166 //  V8_CC_INTEL   - Intel C++
    167 //  V8_CC_MINGW   - Minimalist GNU for Windows
    168 //  V8_CC_MINGW32 - Minimalist GNU for Windows (mingw32)
    169 //  V8_CC_MINGW64 - Minimalist GNU for Windows (mingw-w64)
    170 //  V8_CC_MSVC    - Microsoft Visual C/C++
    171 //
    172 // C++11 feature detection
    173 //
    174 //  V8_HAS_CXX11_ALIGNAS        - alignas specifier supported
    175 //  V8_HAS_CXX11_ALIGNOF        - alignof(type) operator supported
    176 //  V8_HAS_CXX11_STATIC_ASSERT  - static_assert() supported
    177 //  V8_HAS_CXX11_DELETE         - deleted functions supported
    178 //  V8_HAS_CXX11_FINAL          - final marker supported
    179 //  V8_HAS_CXX11_OVERRIDE       - override marker supported
    180 //
    181 // Compiler-specific feature detection
    182 //
    183 //  V8_HAS___ALIGNOF                    - __alignof(type) operator supported
    184 //  V8_HAS___ALIGNOF__                  - __alignof__(type) operator supported
    185 //  V8_HAS_ATTRIBUTE_ALIGNED            - __attribute__((aligned(n))) supported
    186 //  V8_HAS_ATTRIBUTE_ALWAYS_INLINE      - __attribute__((always_inline))
    187 //                                        supported
    188 //  V8_HAS_ATTRIBUTE_DEPRECATED         - __attribute__((deprecated)) supported
    189 //  V8_HAS_ATTRIBUTE_NOINLINE           - __attribute__((noinline)) supported
    190 //  V8_HAS_ATTRIBUTE_UNUSED             - __attribute__((unused)) supported
    191 //  V8_HAS_ATTRIBUTE_VISIBILITY         - __attribute__((visibility)) supported
    192 //  V8_HAS_ATTRIBUTE_WARN_UNUSED_RESULT - __attribute__((warn_unused_result))
    193 //                                        supported
    194 //  V8_HAS_BUILTIN_EXPECT               - __builtin_expect() supported
    195 //  V8_HAS_DECLSPEC_ALIGN               - __declspec(align(n)) supported
    196 //  V8_HAS_DECLSPEC_DEPRECATED          - __declspec(deprecated) supported
    197 //  V8_HAS_DECLSPEC_NOINLINE            - __declspec(noinline) supported
    198 //  V8_HAS___FINAL                      - __final supported in non-C++11 mode
    199 //  V8_HAS___FORCEINLINE                - __forceinline supported
    200 //  V8_HAS_SEALED                       - MSVC style sealed marker supported
    201 //
    202 // Note that testing for compilers and/or features must be done using #if
    203 // not #ifdef. For example, to test for Intel C++ Compiler, use:
    204 //  #if V8_CC_INTEL
    205 //   ...
    206 //  #endif
    207 
    208 #if defined(__clang__)
    209 
    210 # define V8_CC_CLANG 1
    211 
    212 // Clang defines __alignof__ as alias for __alignof
    213 # define V8_HAS___ALIGNOF 1
    214 # define V8_HAS___ALIGNOF__ V8_HAS___ALIGNOF
    215 
    216 # define V8_HAS_ATTRIBUTE_ALIGNED (__has_attribute(aligned))
    217 # define V8_HAS_ATTRIBUTE_ALWAYS_INLINE (__has_attribute(always_inline))
    218 # define V8_HAS_ATTRIBUTE_DEPRECATED (__has_attribute(deprecated))
    219 # define V8_HAS_ATTRIBUTE_NOINLINE (__has_attribute(noinline))
    220 # define V8_HAS_ATTRIBUTE_UNUSED (__has_attribute(unused))
    221 # define V8_HAS_ATTRIBUTE_VISIBILITY (__has_attribute(visibility))
    222 # define V8_HAS_ATTRIBUTE_WARN_UNUSED_RESULT \
    223     (__has_attribute(warn_unused_result))
    224 
    225 # define V8_HAS_BUILTIN_EXPECT (__has_builtin(__builtin_expect))
    226 
    227 # define V8_HAS_CXX11_ALIGNAS (__has_feature(cxx_alignas))
    228 # define V8_HAS_CXX11_STATIC_ASSERT (__has_feature(cxx_static_assert))
    229 # define V8_HAS_CXX11_DELETE (__has_feature(cxx_deleted_functions))
    230 # define V8_HAS_CXX11_FINAL (__has_feature(cxx_override_control))
    231 # define V8_HAS_CXX11_OVERRIDE (__has_feature(cxx_override_control))
    232 
    233 #elif defined(__GNUC__)
    234 
    235 # define V8_CC_GNU 1
    236 // Intel C++ also masquerades as GCC 3.2.0
    237 # define V8_CC_INTEL (defined(__INTEL_COMPILER))
    238 # define V8_CC_MINGW32 (defined(__MINGW32__))
    239 # define V8_CC_MINGW64 (defined(__MINGW64__))
    240 # define V8_CC_MINGW (V8_CC_MINGW32 || V8_CC_MINGW64)
    241 
    242 # define V8_HAS___ALIGNOF__ (V8_GNUC_PREREQ(4, 3, 0))
    243 
    244 # define V8_HAS_ATTRIBUTE_ALIGNED (V8_GNUC_PREREQ(2, 95, 0))
    245 // always_inline is available in gcc 4.0 but not very reliable until 4.4.
    246 // Works around "sorry, unimplemented: inlining failed" build errors with
    247 // older compilers.
    248 # define V8_HAS_ATTRIBUTE_ALWAYS_INLINE (V8_GNUC_PREREQ(4, 4, 0))
    249 # define V8_HAS_ATTRIBUTE_DEPRECATED (V8_GNUC_PREREQ(3, 4, 0))
    250 # define V8_HAS_ATTRIBUTE_DEPRECATED_MESSAGE (V8_GNUC_PREREQ(4, 5, 0))
    251 # define V8_HAS_ATTRIBUTE_NOINLINE (V8_GNUC_PREREQ(3, 4, 0))
    252 # define V8_HAS_ATTRIBUTE_UNUSED (V8_GNUC_PREREQ(2, 95, 0))
    253 # define V8_HAS_ATTRIBUTE_VISIBILITY (V8_GNUC_PREREQ(4, 3, 0))
    254 # define V8_HAS_ATTRIBUTE_WARN_UNUSED_RESULT \
    255     (!V8_CC_INTEL && V8_GNUC_PREREQ(4, 1, 0))
    256 
    257 # define V8_HAS_BUILTIN_EXPECT (V8_GNUC_PREREQ(2, 96, 0))
    258 
    259 // g++ requires -std=c++0x or -std=gnu++0x to support C++11 functionality
    260 // without warnings (functionality used by the macros below).  These modes
    261 // are detectable by checking whether __GXX_EXPERIMENTAL_CXX0X__ is defined or,
    262 // more standardly, by checking whether __cplusplus has a C++11 or greater
    263 // value. Current versions of g++ do not correctly set __cplusplus, so we check
    264 // both for forward compatibility.
    265 # if defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L
    266 #  define V8_HAS_CXX11_ALIGNAS (V8_GNUC_PREREQ(4, 8, 0))
    267 #  define V8_HAS_CXX11_ALIGNOF (V8_GNUC_PREREQ(4, 8, 0))
    268 #  define V8_HAS_CXX11_STATIC_ASSERT (V8_GNUC_PREREQ(4, 3, 0))
    269 #  define V8_HAS_CXX11_DELETE (V8_GNUC_PREREQ(4, 4, 0))
    270 #  define V8_HAS_CXX11_OVERRIDE (V8_GNUC_PREREQ(4, 7, 0))
    271 #  define V8_HAS_CXX11_FINAL (V8_GNUC_PREREQ(4, 7, 0))
    272 # else
    273 // '__final' is a non-C++11 GCC synonym for 'final', per GCC r176655.
    274 #  define V8_HAS___FINAL (V8_GNUC_PREREQ(4, 7, 0))
    275 # endif
    276 
    277 #elif defined(_MSC_VER)
    278 
    279 # define V8_CC_MSVC 1
    280 
    281 # define V8_HAS___ALIGNOF 1
    282 
    283 // Override control was added with Visual Studio 2005, but
    284 // Visual Studio 2010 and earlier spell "final" as "sealed".
    285 # define V8_HAS_CXX11_FINAL (_MSC_VER >= 1700)
    286 # define V8_HAS_CXX11_OVERRIDE (_MSC_VER >= 1400)
    287 # define V8_HAS_SEALED (_MSC_VER >= 1400)
    288 
    289 # define V8_HAS_DECLSPEC_ALIGN 1
    290 # define V8_HAS_DECLSPEC_DEPRECATED (_MSC_VER >= 1300)
    291 # define V8_HAS_DECLSPEC_NOINLINE 1
    292 
    293 # define V8_HAS___FORCEINLINE 1
    294 
    295 #endif
    296 
    297 
    298 // -----------------------------------------------------------------------------
    299 // Helper macros
    300 
    301 // A macro used to make better inlining. Don't bother for debug builds.
    302 // Use like:
    303 //   V8_INLINE int GetZero() { return 0; }
    304 #if !defined(DEBUG) && V8_HAS_ATTRIBUTE_ALWAYS_INLINE
    305 # define V8_INLINE inline __attribute__((always_inline))
    306 #elif !defined(DEBUG) && V8_HAS___FORCEINLINE
    307 # define V8_INLINE __forceinline
    308 #else
    309 # define V8_INLINE inline
    310 #endif
    311 
    312 
    313 // A macro used to tell the compiler to never inline a particular function.
    314 // Don't bother for debug builds.
    315 // Use like:
    316 //   V8_NOINLINE int GetMinusOne() { return -1; }
    317 #if !defined(DEBUG) && V8_HAS_ATTRIBUTE_NOINLINE
    318 # define V8_NOINLINE __attribute__((noinline))
    319 #elif !defined(DEBUG) && V8_HAS_DECLSPEC_NOINLINE
    320 # define V8_NOINLINE __declspec(noinline)
    321 #else
    322 # define V8_NOINLINE /* NOT SUPPORTED */
    323 #endif
    324 
    325 
    326 // A macro to mark classes or functions as deprecated.
    327 #if defined(V8_DEPRECATION_WARNINGS) && V8_HAS_ATTRIBUTE_DEPRECATED_MESSAGE
    328 # define V8_DEPRECATED(message, declarator) \
    329 declarator __attribute__((deprecated(message)))
    330 #elif defined(V8_DEPRECATION_WARNINGS) && V8_HAS_ATTRIBUTE_DEPRECATED
    331 # define V8_DEPRECATED(message, declarator) \
    332 declarator __attribute__((deprecated))
    333 #elif defined(V8_DEPRECATION_WARNINGS) && V8_HAS_DECLSPEC_DEPRECATED
    334 # define V8_DEPRECATED(message, declarator) __declspec(deprecated) declarator
    335 #else
    336 # define V8_DEPRECATED(message, declarator) declarator
    337 #endif
    338 
    339 
    340 // A macro to mark variables or types as unused, avoiding compiler warnings.
    341 #if V8_HAS_ATTRIBUTE_UNUSED
    342 # define V8_UNUSED __attribute__((unused))
    343 #else
    344 # define V8_UNUSED
    345 #endif
    346 
    347 
    348 // Annotate a function indicating the caller must examine the return value.
    349 // Use like:
    350 //   int foo() V8_WARN_UNUSED_RESULT;
    351 #if V8_HAS_ATTRIBUTE_WARN_UNUSED_RESULT
    352 # define V8_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
    353 #else
    354 # define V8_WARN_UNUSED_RESULT /* NOT SUPPORTED */
    355 #endif
    356 
    357 
    358 // A macro to provide the compiler with branch prediction information.
    359 #if V8_HAS_BUILTIN_EXPECT
    360 # define V8_UNLIKELY(condition) (__builtin_expect(!!(condition), 0))
    361 # define V8_LIKELY(condition) (__builtin_expect(!!(condition), 1))
    362 #else
    363 # define V8_UNLIKELY(condition) (condition)
    364 # define V8_LIKELY(condition) (condition)
    365 #endif
    366 
    367 
    368 // A macro to specify that a method is deleted from the corresponding class.
    369 // Any attempt to use the method will always produce an error at compile time
    370 // when this macro can be implemented (i.e. if the compiler supports C++11).
    371 // If the current compiler does not support C++11, use of the annotated method
    372 // will still cause an error, but the error will most likely occur at link time
    373 // rather than at compile time. As a backstop, method declarations using this
    374 // macro should be private.
    375 // Use like:
    376 //   class A {
    377 //    private:
    378 //     A(const A& other) V8_DELETE;
    379 //     A& operator=(const A& other) V8_DELETE;
    380 //   };
    381 #if V8_HAS_CXX11_DELETE
    382 # define V8_DELETE = delete
    383 #else
    384 # define V8_DELETE /* NOT SUPPORTED */
    385 #endif
    386 
    387 
    388 // Annotate a virtual method indicating it must be overriding a virtual
    389 // method in the parent class.
    390 // Use like:
    391 //   virtual void bar() V8_OVERRIDE;
    392 #if V8_HAS_CXX11_OVERRIDE
    393 # define V8_OVERRIDE override
    394 #else
    395 # define V8_OVERRIDE /* NOT SUPPORTED */
    396 #endif
    397 
    398 
    399 // Annotate a virtual method indicating that subclasses must not override it,
    400 // or annotate a class to indicate that it cannot be subclassed.
    401 // Use like:
    402 //   class B V8_FINAL : public A {};
    403 //   virtual void bar() V8_FINAL;
    404 #if V8_HAS_CXX11_FINAL
    405 # define V8_FINAL final
    406 #elif V8_HAS___FINAL
    407 # define V8_FINAL __final
    408 #elif V8_HAS_SEALED
    409 # define V8_FINAL sealed
    410 #else
    411 # define V8_FINAL /* NOT SUPPORTED */
    412 #endif
    413 
    414 
    415 // This macro allows to specify memory alignment for structs, classes, etc.
    416 // Use like:
    417 //   class V8_ALIGNED(16) MyClass { ... };
    418 //   V8_ALIGNED(32) int array[42];
    419 #if V8_HAS_CXX11_ALIGNAS
    420 # define V8_ALIGNED(n) alignas(n)
    421 #elif V8_HAS_ATTRIBUTE_ALIGNED
    422 # define V8_ALIGNED(n) __attribute__((aligned(n)))
    423 #elif V8_HAS_DECLSPEC_ALIGN
    424 # define V8_ALIGNED(n) __declspec(align(n))
    425 #else
    426 # define V8_ALIGNED(n) /* NOT SUPPORTED */
    427 #endif
    428 
    429 
    430 // This macro is similar to V8_ALIGNED(), but takes a type instead of size
    431 // in bytes. If the compiler does not supports using the alignment of the
    432 // |type|, it will align according to the |alignment| instead. For example,
    433 // Visual Studio C++ cannot combine __declspec(align) and __alignof. The
    434 // |alignment| must be a literal that is used as a kind of worst-case fallback
    435 // alignment.
    436 // Use like:
    437 //   struct V8_ALIGNAS(AnotherClass, 16) NewClass { ... };
    438 //   V8_ALIGNAS(double, 8) int array[100];
    439 #if V8_HAS_CXX11_ALIGNAS
    440 # define V8_ALIGNAS(type, alignment) alignas(type)
    441 #elif V8_HAS___ALIGNOF__ && V8_HAS_ATTRIBUTE_ALIGNED
    442 # define V8_ALIGNAS(type, alignment) __attribute__((aligned(__alignof__(type))))
    443 #else
    444 # define V8_ALIGNAS(type, alignment) V8_ALIGNED(alignment)
    445 #endif
    446 
    447 
    448 // This macro returns alignment in bytes (an integer power of two) required for
    449 // any instance of the given type, which is either complete type, an array type,
    450 // or a reference type.
    451 // Use like:
    452 //   size_t alignment = V8_ALIGNOF(double);
    453 #if V8_HAS_CXX11_ALIGNOF
    454 # define V8_ALIGNOF(type) alignof(type)
    455 #elif V8_HAS___ALIGNOF
    456 # define V8_ALIGNOF(type) __alignof(type)
    457 #elif V8_HAS___ALIGNOF__
    458 # define V8_ALIGNOF(type) __alignof__(type)
    459 #else
    460 // Note that alignment of a type within a struct can be less than the
    461 // alignment of the type stand-alone (because of ancient ABIs), so this
    462 // should only be used as a last resort.
    463 namespace v8 { template <typename T> class AlignOfHelper { char c; T t; }; }
    464 # define V8_ALIGNOF(type) (sizeof(::v8::AlignOfHelper<type>) - sizeof(type))
    465 #endif
    466 
    467 #endif  // V8CONFIG_H_
    468